"I first met Amy Schumer almost six years ago when she came in to audition for the role of Shoshanna on 'Girls,'" Dunham wrote on her site Lenny. "Everyone in the room was stunned by the detail and skill of her improv, the wild talent radiating off her (and I was personally intrigued by her breasts)."

Despite blowing away the room, Schumer didn't get the role. It eventually went to Zosia Mamet, whose unique portrayal of Shoshanna makes it hard to imagine anyone else in the role now. Dunham said that Schumer just didn't seem right for the role.

"It was clear Amy wasn't meant to play an innocent Juicy Couture lover obsessed with emoji — even if her Meatpacking District club lingo was the funniest s--- I had ever heard," Dunham said. "But when she left the room, the vibe was very 'Someone give that lady a show, STAT!'"

Dunham says she never forgot Schumer's audition. And eventually, the comedian did appear on "Girls."

"A year later, we couldn't get her off our minds and asked Amy to come back and play a pivotal role as the protective best friend of Adam's new GF, a lady with a penchant for gold lamé and verbal threats," Dunham recalled. "Our entire crew was in stitches, even if she was just dancing across a background shot. There was also something so tender about her portrayal."

Schumer currently stars on her own Emmy-nominated Comedy Central sketch show, "Inside Amy Schumer," which she cocreated, writes, and produces. Last year, she starred in the movie "Trainwreck."